January 13, 2007 12:01pm CST
Translate this: Cluck cluck. Tck tck. Squawk. Get it? If you were a chicken, you might. According to new research, chickens make meaningful sounds that refer to objects around them. A pecking chicken that goes "tck, tck, tck," for example, is saying, "Hey look, there's food!" (You can hear a chicken's food calls at http://www.sciencenews.org/20061118/foodcall.aif .) The discovery marks the first time that an animal other than people, monkeys, and other primates has been found to make sounds that, like words, represent something in the world around them. The existence of word-like clucks is not a total surprise to scientists. Previous studies had shown that male chickens make certain clucking noises when they find food. When female chickens (hens) hear these noises, they stomp over and either take some food from a male's beak or stare at the ground looking for morsels to eat. "They look like people who've lost their glasses," says Chris Evans of Macquarie University in Sydney, Australia. Other studies had also shown, for example, that chickens make alarm calls when scared by an intruder. The calls differ depending on whether the intruder walks or flies toward them. And other chickens react by looking either up in the air or around on the ground. This behavior did not necessarily prove that a cluck works like a word that refers to some object around the bird, Evans says. Instead, it was possible that the noise simply triggers a reflex in the birds to, for example, start pecking for supper. To investigate further, researchers conducted a number of food-based trials. In half of the tests, the scientists allowed hens to find three kernels of corn—not enough to fill the animals up, but enough to alert them that food was around. "The corn is like chocolate for them," Evans says. In the other half of the tests, the hens didn't get a treat. Next, the scientists played recordings of male food calls for the hens. In response, hens that already knew food was available looked at the ground for just 3 seconds. Food-deprived hens, on the other hand, searched for an average of 7.5 seconds after hearing the male calls. On the other hand, when the hens heard alarm calls, both fed and unfed birds reacted in the same way. These results suggest that the food-searching response is not a reflex, the researchers say. Instead, the birds seem to know what the food call means, and their reaction depends on what they already know about the area's food supply Now try again: tck, tck, tck. Feeling hungry, yet?